I found that even with a 7dBi antenna the GC wasn't much improved in my new house - which interestingly is plaster and lath walls covered by 3/8" drywall. So, the environment can have a tremendous effect. Have you tried moving the router up/down, to a different room (if possible)?

I have it in my bedroom. Across the house (drywall and wood studs) the reception is flaky, when I sit on the couch I must face such that my back is not to the router or the connection will drop and speed will be very unreliable. When I turn so my body is out of the way it's fairly reliable. I wanted to make this particular area more stable with the antenna. When I put the antenna in, and take it out there is no difference @ all in Net Stumbler from any position in my living room or even in my bedroom. Nothing @ all.

Can you measure your antenna for me?? Mine says that it's 50 ohms. I measureed it with an ohmeter from the centre to the threads and the resistance is infinity (no connection @ all) I was wondering if there's a "setting" to change from internal to external antenna. I tried unplugging the power and it made no difference.

No good measuring with an ohm-meter - that reads the DC Resistance of the antenna (wich is usually either infinity, or close to zero!) The 50 ohms is the impedance (AC resistance) at 2.5GHz.

So probably nothing like that wrong with the antenna. It's a somewhat more expensive solution, but maybe you should think about getting a range extender (WRE) and trying to find somewhere that you can place it to assist these difficult spots.

Another solution might be to try having someone hold your router up nice and high - there tends to be more "stuff" blocking signals at lower levels (furniture, people). If that helps, then get a shelf to mount it on!